Maintaining water quality

For applications like desalination and wastewater reuse, maintenance and continuous plant condition monitoring are of utmost importance to ensure that all risks are properly managed. Major risks of a poorly operated and maintained membrane plant include:

producing water unfit for human consumption

the risk of breakdown

inability to be online for water production

unnecessary plant damage

shorter membrane lifespans, resulting in

higher operating costs.

Continuous monitoring of a plant ensures that key performance indicators relating to water quality are maintained and that early warning is given when these parameters start to drift. Such performance indicators may include online turbidity measurement in case of solids removal, conductivity in case of salt removal (treatment of brackish water or sea water), and residual chlorine where disinfection is required, to name a few.

Continuous monitoring provides early warning to enable automatic plant shutdown in the case of non-conformity, preventing non-compliant water from being delivered to consumers. Equipment damage can also be prevented with online monitoring and alarm points for immediate shutdown.

Quality analysis

In association with continuous plant monitoring, regular samples need to be taken by an independent laboratory to verify and confirm operational conditions. This is required for both feedwater and product water to ensure that all indicators remain compliant, and to monitor changes in the feedwater. This may warrant changes to plant equipment or conditions to ensure that the plant can continue to treat the feedwater.

A water treatment plant is designed for a specific feedwater and can accommodate limited changes in quality. A lack of feedwater quality monitoring may result in non-compliant final water or damage to plant equipment.

In addition to continuous monitoring, regular preventative maintenance is of utmost importance. The instrumentation requires cleaning and calibration to ensure accurate measurements. Treatment technologies, such as ultrafiltration membranes and reverse osmosis membranes, also require periodic cleaning. Failure to do so will result in the malfunctioning of the membrane, rendering the plant ineffective in removing unwanted constituents.

Mechanical equipment, such as valves and pumps, must be inspected on a routine maintenance schedule. During pump maintenance early warning signs of worn bearings, worn seals or condensation damage to motors must be identified, so that replacement units can be arranged in advance. If a pump breaks down and spare parts are not readily available, the plant may be inoperative for an extended period, resulting in no water being produced.

Advanced technologies, like membrane based plants, require a specialist operator for the continuous monitoring and maintenance schedules. Many times, new technologies get a ‘bad rap’ as a result of incorrect operation and maintenance by inexperienced staff.

“QFS endeavours to impart as much knowledge to the operators during handover and training to ensure correct operation,” says Herman Smit, managing director, Quality Filtration Systems (QFS). “We’re also available to support clients in the operation and maintenance of the plants through a service level agreement, customised to their requirements.

“As the applications for advanced technologies increase in a water-scarce country like South Africa, so should our skill level improve to correctly operate and maintain plants that will ensure our water security in the future,” he concludes.

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